US 7921661 B2
A refrigerant cycle is provided with a multi-port compressor or compressor stages connected in series, and multiple condensers. A single evaporator communicates with the plurality of condensers. At least one of the plurality of condensers receives fully compressed refrigerant while the other condensers receive refrigerant at intermediate pressure. A control can optionally direct refrigerant to the condensers to achieve desired system heat rejection characteristics and operating conditions. One or multiple reheat coils may be associated with the evaporator and are arranged either in series or in parallel to provide a desired dehumidification function and reheat stages. One or several of the intermediate pressure condensers may be utilized for the reheat function as well.
1. A refrigerant system comprising:
at least one compressor delivering a refrigerant to a first condenser from a discharge line and at a relatively high pressure, said refrigerant from said first condenser passing through an expansion device, and downstream to an evaporator, said refrigerant from said evaporator returning to said compressor; and
an intermediate pressure tap for tapping said refrigerant from said compressor at an intermediate compression point, the tapped refrigerant being at a relatively low pressure compared to said relatively high pressure, said refrigerant from said intermediate pressure tap passing through a second condenser, said refrigerant having passed through said second condenser passing through an expansion device and to said evaporator, and from said evaporator back to said compressor; and
a reheat coil associated with said evaporator.
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15. A method of operating a refrigerant system comprising the steps of:
1) delivering a compressed refrigerant to a first condenser from at least one compressor having an intermediate pressure tap for delivering a partially compressed refrigerant to a second condenser, said refrigerant from both said first and second condensers passing through a common evaporator and back to at least said one compressor, and providing a reheat coil associated with said evaporator; said compressed refrigerant delivered to said first condenser being at a higher pressure than the partially compressed refrigerant delivered to the second condenser; and
2) operating said refrigerant cycle by selectively routing said refrigerant from said at least one compressor to said first and second condensers and selectively directing said refrigerant to said reheat coil.
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This application relates to a refrigerant system having a common evaporator, but separate condensers where at least one of the condensers is connected to an intermediate pressure compression stage, while the other condenser is connected to a high pressure compression stage, and wherein a reheat coil is incorporated into the refrigerant cycle.
Refrigerant systems are utilized in applications to change the temperature and humidity or otherwise condition the environment. In a standard refrigerant system, a compressor delivers a compressed refrigerant to a heat exchanger, known as a condenser, which is typically located outside. From the condenser, the refrigerant passes through an expansion device, and then to an indoor heat exchanger, known as an evaporator. At the evaporator, moisture may be removed from the air, and the temperature of air blown over the evaporator coil is lowered. From the evaporator, the refrigerant returns to the compressor. Of course, basic refrigerant cycles are utilized in combination with many configuration variations and optional features. However, the above provides a brief understanding of the fundamental concept.
Refrigerant cycles are known, wherein a so-called economizer circuit is incorporated. In an economizer circuit, a first refrigerant line is tapped from a main refrigerant line downstream of the condenser. The tapped refrigerant line is passed through an expansion device, and then the tapped refrigerant and the main refrigerant both flow through an economizer heat exchanger. The tapped refrigerant subcools the main refrigerant, such that when the main refrigerant reaches an evaporator, it will have a greater cooling potential. The tapped refrigerant, having subcooled the main refrigerant, is returned to the compressor at an intermediate compression point.
In some cases, while the system is operating in a cooling mode, the temperature level at which the air is delivered to provide a comfort environment in a conditioned space may need to be higher than the temperature that would provide the ideal humidity level. Generally, lower the temperature of the air stream more moisture can be removed from this air stream. However, lowering the air temperature below certain level is undesirable. This has presented challenges to refrigerant system designers. One way to address such challenges is to utilize various schematics incorporating reheat coils that will increase the air temperature. In many cases, a reheat coil placed in the way of an indoor air stream behind the evaporator is employed for the purposes of reheating the air supplied to the conditioned space after it has been cooled in the evaporator, and where the moisture has been removed.
While reheat coils have been incorporated into air conditioning systems, they have not been utilized in an air conditioning system having an ability to reject heat at multiple temperature levels.
The present invention employs the flow of refrigerant from an intermediate compression point in a compressor to selectively provide refrigerant to at least one of a plurality of condensers, where each of the condensers operate at different temperature levels. In this manner, the heat rejection characteristics of the refrigerant cycle can be controlled to provide enhanced flexibility to a refrigerant cycle designer. Also, improved dehumidification function is provided by incorporating a reheat coil into the refrigerant system.
In the proposed system design, a portion of the refrigerant, compressed to some intermediate pressure, leaves the compressor through an intermediate compressor port, while the rest of the refrigerant vapor continues through the compression process to a main discharge port and then to a first (main) condenser. The refrigerant that leaves the intermediate port is connected to another (second) condenser. Consequently, for such a system an additional temperature level of heat rejection is available. Such heat rejection capability at various temperature levels can be utilized in multiple industrial applications where condensers are located in different environments. For example, the main condenser can be located outdoors, while the second condenser is located indoors. Another application would be for heat pump installations, where there are two environmental chambers each requiring a different amount of heating. The amount of refrigerant flowing through each condenser can be regulated by expansion devices, as explained below. In the present invention, a refrigerant system is provided with a common evaporator receiving refrigerant from at least two condensers. The evaporator is associated with one or more reheat coils.
In several embodiments, there may be more than one compressor connected in series, or a single compressor can selectively deliver refrigerant to the two condensers. In case of several compressors connected in series, the intermediate port, as described above, can simply be positioned in a line connecting the lower pressure compressor to a higher pressure compressor.
In yet another embodiments, there may be more than two condensers operating at more than two different temperature levels.
In still another embodiments, one of the condensers itself may be utilized for the reheat function.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A control 37 controls the various devices and components in the refrigerant system 20 to achieve the desired characteristics.
The system described above is disclosed and claimed in U.S. patent application Ser. No. 10/963484, filed on Oct. 12, 2004, now U.S. Pat. No. 7,131,285, and entitled “Refrigerant Cycle With Plural Condensers Receiving Refrigerant at Different Pressures.”
In addition, the present invention incorporates a reheat coil 52 into the refrigerant system 20. As shown, a three-way valve 50 selectively taps refrigerant from a main refrigerant flow line through the reheat coil 52. Downstream of the reheat coil 52, the refrigerant passes through a check valve 54, and rejoins the refrigerant in the main circuit at a point 56 downstream of the three-way valve 50. As is known, the reheat coil 52 is positioned to be in the path of flow of air driven by an air-moving device such as fan F having moved air over the evaporator 32 and toward the environment to be conditioned. As is known, the air is cooled and dehumidified in the evaporator 32, and may be cooled to a temperature below that which would be desirable for an environment to be conditioned.
The air is reheated above the temperature imparted to the air in the evaporator 32 by the relatively hot refrigerant in the reheat coil 52 to provide a desired comfort temperature level in the environment to be conditioned.
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In addition, a bypass line 58 and a shut-off valve 60 allows refrigerant to bypass the condenser 26. This option is utilized when dehumidification is desired without significant cooling. A worker of ordinary skill in the art would recognize how to utilize the control 37 to selectively operate the bypass valve 60 to achieve a desired system condition.
As known, all flow control devices such as the three-way valve 50 and valves 28 and 60 may be of a conventional shut-off or adjustable type. Also, the three-way valve 50 may be substituted by a pair of conventional valves.
Of course, many modifications of these two disclosed schematics are possible. Alternatives to the three-way valves may be utilized, and various locations for tapping the refrigerant to the reheat coil may be employed. In other words, the specifics of the reheat schematic is not essential here and is transparent to the teachings of this invention. The combination of condensers operating at different temperature levels and a reheat function is inventive and beneficial for the system operation, control, and application coverage.
Of course, other multiples of compressors and compressor banks as well as condensers operating at various temperature levels can be utilized within the scope of this invention. Also, a single compressor may have more than one intermediate pressure tap or multiple compression stages may be connected in series, providing capability for the system to operate at multiple temperature levels.
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Although preferred embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.